Multi-antenna distribution of wireless broadband in a building

ABSTRACT

The disclosed embodiments include methods and systems for distributing a broadband wireless signal in a building. The disclosed methods and systems feature a wireless broadband transmitter associated with multiple base antennas, where the base antennas are inserted into one or more ducts of the ventilation system of the building. Communication between the transmitter and receivers within the building may be optimized by selecting, modifying or controlling a configuration parameter of at least one of the multiple base antennas to enhance distribution of the wireless broadband signal within the ducts of the ventilation system and between the transmitter and device receivers.

COPYRIGHT STATEMENT

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

FIELD

The present disclosure relates, in general, to systems and methods fordistributing wireless broadband signals throughout a building and moreparticularly to the use of optimized multi-antenna distribution methodsand systems in conjunction with using the building HVAC ducts as awaveguide system.

BACKGROUND

The wireless distribution of broadband signals within a building isbecoming commonplace. Wi-Fi is now the most common way people access theInternet. Smart phones compliant with 3G and 4G standards are commonlyused inside buildings. Personal computers, laptop computers, cellularphones, tablet computers, PDAs and other portable devices are typicallyconfigured to receive a wireless broadband signal. In addition,televisions, DVD players, Blu-ray disc players, smart thermostats,printers, copiers and many other digitally enabled home or businessappliances are configured for wireless network access. To meet the needsof these and similar devices, many buildings now include a wirelessaccess point (WAP), base station or repeater connected to a local orexternal network to send and receive data or communication signals toand from wireless devices within or near the building.

Prior to the advent of local wireless networks, a home or business ownerwas required to run cables through walls and ceilings to deliver networkaccess to any network enabled devices within the building. Now, abuilding owner may have wired access to the Internet, a LAN or anothernetwork at one specific location within a building and simply install awireless router or other type of WAP to more easily extend the networkto end-user devices. A WAP is built to support a standard for sendingand receiving data using radio frequencies. The standards and thedesignated transmission frequencies used are defined by the IEEE. Manywireless access points use the 802.11a/b/g/n, or 802.11ac/ad standard.

Other types of networks, cellular telephone networks for example,feature a wireless signal originating outside of the building. Thewalls, floors and other structures of the building can attenuate ordegrade the original wireless signal sufficiently to cause accessproblems for cellular telephone users within a building. Thus,femtocells, wireless repeater devices, or other wireless networkelements can be installed within a building to transmit certain wirelesssignal locally. Many of these wireless network elements use LTE, or LTEAdvanced standards

One problem with the transmission of wireless broadband signals within abuilding is difficulty obtaining a sufficiently strong communicationchannel between the WAP or repeater and various receiving devices. Forexample, the popular Wi-Fi standard defined in IEEE 802.11b is a lowpowered solution (less than 1 W) having a range of no more than 300 feetfrom the transmitter. The closer a receiving device is to thetransmitter the better chance the receiver will have of connecting andtypically the faster the Wi-Fi uplink/downlink performance will be.Connectivity and signal strength problems can be exacerbated by thewalls, floors, ceilings and other surfaces or barriers present in atypical building which can cause signal attenuation and reflection.

One solution to this problem is to provide duplicate WAPs distributedthroughout a building with each WAP directly connected to the wirednetwork or repeater. This solution however involves the cost andinconvenience of duplicate WAPs and additional cabling. Another solutionis the use of wireless range extenders or signal boosters

Another solution to the problem of insufficiently reliable communicationbetween a WAP and various receiving devices is based upon advancedantenna technology. For example, multiple input/multiple output (MIMO)is a wireless technology which employs multiple intelligent radioantennas to improve transmission speed and the quality of wirelessnetwork transmissions over longer distances than might otherwise bepossible. Enhanced antenna technology may certainly improve thereliability, speed and range of wireless broadband communication withina building. Nonetheless, any wireless system will at some point belimited by the distance between the WAP and wireless devices, whichlimitations are exacerbated by the walls, floors, ceilings and othersurfaces or structures always present in a building.

U.S. Pat. No. 6,980,768 teaches the use of a building ventilation systemas a waveguide to enhance the distribution of a spread spectrum signalwithin a building, in particular a code division multiple access (CDMA)telecommunications signal. The U.S. Pat. No. 6,980,768 describes how theducts of a conventional ventilation system can operate as waveguides.Bends, kinks, rough surfaces, splits, and variations in duct size orconfiguration will inevitably cause fading in any RF signal transmittedthrough a duct waveguide. The spread spectrum nature of the signaldescribed in the U.S. Pat. No. 6,980,768 provides little opportunity fortransmission optimization within a ventilation system. Hence, there is aneed for solutions that can overcome some or all of the technicalhurdles identified above to allow the effective distribution andoptimization of the distribution of broadband wireless signals in abuilding.

BRIEF SUMMARY

Certain embodiments disclosed herein include methods of distributing abroadband wireless signal in a building. The disclosed methods includethe steps of providing a transmitter operatively associated withmultiple base antennas, where the base antennas are inserted into one ormore ducts of the ventilation system of the building. In addition, themethods may include providing one or more receivers operativelyassociated with one or more devices having device antennas. Thereceivers may be devices such as cellular telephones, computers or otherwireless enabled apparatus located anywhere in or near the building.Communication between the transmitter and receivers may be optimized byselecting, modifying or controlling a configuration parameter of atleast one base antenna to enhance distribution of the wireless broadbandsignal within the ducts of the ventilation system and between thetransmitter and device receivers.

Thus, the disclosed method embodiments generally include steps ofselecting, optimizing, implementing or otherwise setting a configurationparameter of one or multiple base antennas. The configuration parametermay be, but is not limited to a physical antenna parameter such as thelocation of the base antenna(s) or the angular orientation of the baseantenna(s) with respect to a duct surface or with respect to otherantennas. In addition, the configuration parameter might be a signalattribute, including but not limited to transmission signal phase,transmission signal amplitude or transmission signal preconditioning.Accordingly, the communication of the wireless broadband signal betweenthe transmitter and the receiver(s) might be enhanced by optimizing thepropagation of the wireless broadband signal within the ventilationsystem by optimizing the transmission mode or otherwise; optimizingde-correlation between at least two signal paths between at least twobase antennas and one or more device antennas; optimizing a correlationmatrix between at least two base antennas and at least two deviceantennas or other techniques.

In one non-limiting example, the configuration parameter of the adjustedbase antenna is selected to favor a first selected hollow waveguidepropagation mode. Optionally, the configuration parameter of a secondadjusted base antenna is selected to favor a second selected hollowwaveguide propagation mode which is different than the first selectedhollow waveguide propagation mode. This type of optimization emphasizesde-correlation between the propagation modes.

The configuration parameter can be initially determined empirically andan initial antenna placement or signal attribute may be optimized basedupon the initial determination. Optionally or additionally, the initialconfiguration parameter can be adjusted, supplemented or otherwisemodified based upon a signal parameter of the wireless broadband signalas actually received by the receiver. The foregoing empirical andfeedback-based optimization strategies can be implemented in conjunctionwith each other and may be implemented once, several times orcontinuously.

Alternative embodiments disclosed herein include building-basedcommunications systems including a ventilation system having ducts andopenings within a building, one or multiple receiver devices with one ormore device antennas and a transmitter operatively associated withmultiple base antennas. In the system embodiments, the base antennas, orthe transmitter itself, are inserted into one or more ducts of theventilation system. The transmitter is therefore configured tocommunicate by means of a wireless broadband signal through the multiplebase antennas to one or more receivers with the conducting walls of theventilation system operating as waveguides. The system embodiments maybe used to implement the configuration parameter selection andoptimization techniques noted above to enhance communication of wirelessbroadband signals between the transmitter and a receiver.

In certain system embodiments the selection or optimization of aconfiguration parameter is implemented autonomously orsemi-autonomously. Is such an embodiment, the system will also include aprocessor and a non-transitory machine readable medium encoding a set ofinstructions executable by the processor to perform various steps of themethods noted above.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of particularembodiments may be realized by reference to the remaining portions ofthe specification and the drawings, in which like reference numerals areused to refer to similar components. In some instances, a sub-label isassociated with a reference numeral to denote one of multiple similarcomponents. When reference is made to a reference numeral withoutspecification to an existing sub-label, it is intended to refer to allsuch multiple similar components.

FIG. 1 is a schematic diagram illustrating a simple prior art MIMOsystem.

FIG. 2 is a schematic diagram illustrating a system providing foroptimized wireless communication within a building, in accordance withvarious embodiments.

FIG. 3 is a schematic diagram illustrating the transmitter, antenna andduct portions of a system providing for optimized wireless communicationwithin a building, in accordance with various embodiments.

FIG. 4 is a schematic diagram illustrating an alternative configurationof the transmitter, antenna and duct portions of a system providing foroptimized wireless communication within a building, in accordance withvarious embodiments.

FIG. 5 is a schematic diagram illustrating an alternative configurationof the transmitter, antenna and duct portions of a system providing foroptimized wireless communication within a building, in accordance withvarious embodiments.

FIG. 6 is a process flow diagram illustrating a method of providingoptimized wireless communication within a building, in accordance withvarious embodiments.

FIG. 7 is a process flow diagram illustrating an alternative method ofproviding optimized wireless communication within a building, inaccordance with various embodiments.

FIG. 8 is a process flow diagram illustrating an alternative method ofproviding optimized wireless communication within a building, inaccordance with various embodiments.

FIG. 9 is a schematic diagram illustrating a processing system, inaccordance with various embodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

While various aspects and features of certain embodiments have beensummarized above, the following detailed description illustrates a fewexemplary embodiments in further detail to enable one of skill in theart to practice such embodiments. The described examples are providedfor illustrative purposes and are not intended to limit the scope of theinvention.

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the described embodiments. It will be apparent to oneskilled in the art, however, that other embodiments of the present maybe practiced without some of these specific details. In other instances,certain structures and devices are shown in block diagram form. Severalembodiments are described herein, and while various features areascribed to different embodiments, it should be appreciated that thefeatures described with respect to one embodiment may be incorporatedwith other embodiments as well. By the same token, however, no singlefeature or features of any described embodiment should be consideredessential to every embodiment of the invention, as other embodiments ofthe invention may omit such features.

Unless otherwise indicated, all numbers used herein to expressquantities, dimensions, and so forth used should be understood as beingmodified in all instances by the term “about.” In this application, theuse of the singular includes the plural unless specifically statedotherwise, and use of the terms “and” and “or” means “and/or” unlessotherwise indicated. Moreover, the use of the term “including,” as wellas other forms, such as “includes” and “included,” should be considerednon-exclusive. Also, terms such as “element” or “component” encompassboth elements and components comprising one unit and elements andcomponents that comprise more than one unit, unless specifically statedotherwise.

I. General System and Method Description

One set of embodiments includes systems and methods that provide for theeffective distribution of broadband wireless signals within a building.In general, the embodiments disclosed herein feature the distribution ofbroadband wireless signals in part through the heating, ventilation andair-conditioning (HVAC) system of a building. A typical HVAC systemincludes extensive ductwork, air inlets, air outlets, fans, heaters, airconditioners, humidifiers, dehumidifiers and other apparatus designed tocondition and move air throughout a building. All of the foregoingelements are collectively referred to herein as a ventilation system.The ducts of a building ventilation system can be adapted for use ashollow waveguides as described in detail below.

In addition to leveraging the ventilation system of a building as asystem of hollow waveguides, the disclosed embodiments feature the useof multiple antenna technology. These two separate technologies aresynergistic. In particular the use of a building ventilation system as asystem of hollow waveguides provides for unique optimization strategieswhich cannot be replicated with normal, non-waveguided multiple antennatransmissions.

The disclosed system embodiments will include at least one wirelessaccess point (WAP), repeater or other device including a transmitter.The transmitter will be associated with multiple antennas. Theseantennas are referred to herein as “base” antennas since the transmitteris conveniently described as the base station of a wireless network. Thebase antennas are positioned within the building ventilation system asdescribed in detail below. The transmitter communicates wirelessly withany number of wireless devices positioned in various rooms or spacesthroughout the building. These wireless devices also include one or moreantennas. The antennas associated with wireless devices are referred toherein as “device” antennas to avoid confusion with the base antennas.It is important to note however that typical wireless communicationincludes both uplink and downlink components. Thus, the transmitter isconfigured to both transmit and receive wireless signals through thebase antennas and each device is configured to both transmit and receivewireless signals through one or more device antennas.

The disclosed systems and methods feature the initial selection of, andpotentially the modification of, a configuration parameter of at leastone base antenna to enhance communication of the wireless broadbandsignal from the transmitter through the ventilation system to one ormore receivers. As defined herein a configuration parameter can relateto a physical aspect of a base antenna or an attribute of thetransmitted signal. For example, an antenna configuration parameter canbe, but is not limited to, a selected physical location of an antennawith respect to a duct surface or another antenna. Similarly, aconfiguration parameter may be the angular orientation of the antennawith respect to a duct surface or another antenna. A configurationparameter may also relate to a transmitted signal attribute and can bebut is not limited to the wireless signal phase or the wireless signalamplitude.

As noted above, the disclosed embodiments feature enhanced communicationof a wireless broadband signal from the transmitter to a receiver.Signal or transmission enhancement may occur through one or multiplemeans, including but not limited to; optimizing the propagation of thewireless broadband signal within the ventilation system, optimizingde-correlation between at least two signal paths between base and deviceantennas or optimizing a correlation matrix between multiple baseantennas and multiple device antennas. Each of the above methods ofsignal communication enhancement is discussed in detail herein.

II. Waveguide Transmission Modes

The properties of electromagnetic waves propagating in hollow conductingwaveguides having rectangular or circular cross-sections are well-known.The ducts found in a typical building ventilation system usually havecircular or rectangular cross-sections. Therefore, one method ofoptimizing the propagation of wireless broadband signals propagatingwithin a ventilation system includes placing or orienting multiple baseantennas to favor one or more transmission or propagation modes.

TE modes (transverse electric) have no electric field in the directionof propagation. TM modes (transverse magnetic) have no magnetic field inthe direction of propagation. In rectangular waveguides, mode numbersare designated by two suffix designations attached to the mode type, inthe form TE_(mn), where m is the number of half-wavelengths across thewidth of the waveguide and n is the number of half-wavelengths acrossthe height of the waveguide. In circular waveguides, circular modesexist. Circular mode numbers are also designated in the form TE_(mn) buthere m is the number of half-wavelengths along a half-circumference andn is the number of half-wavelengths along a radius.

Waveguide propagation modes depend upon the operating wavelength and thesize and shape of the guide. Each mode is characterized by a cutofffrequency below which the mode cannot exist in the guide. For example,the cutoff frequency of a rectangular waveguide may be calculatedaccording to the following formula:

$\begin{matrix}{f_{e_{mn}} = {\frac{1}{2\sqrt{\mu ɛ}}\sqrt{\left( \frac{m}{a} \right)^{2} + \left( \frac{n}{b} \right)^{2}}}} & (1)\end{matrix}$Where (a) is the width of the waveguide and (b) is the height of thewaveguide. Waves having frequencies above the cutoff frequencies of morethan one mode can propagate in multiple modes.

Field representations of selected TE and TM modes possible in arectangular or circular waveguide having conducting walls are wellknown. As noted above, in both rectangular and circular cross-sectionwaveguides, the parameter which determines the cutoff frequency for agiven mode is the width or diameter of the waveguide/duct. Thus, themaximum wavelength for a given signal transmitted in a specific duct canbe calculated. More importantly, as detailed below, transmissions atsuitably higher frequencies can be coupled to a duct waveguide in aspecific manner to induce higher order modes which can enhance signaltransmission through a somewhat convoluted and varying duct system.

II. Multiple Antenna Technologies

In conjunction with optimization to favor one or more transmissionmodes, configuration parameters may be adjusted to optimize thetransmission relationship between multiple base antennas and one or moredevice antennas.

Thus, the disclosed systems and methods feature the use of multiple baseantennas associated with the transmitter and one or multiple antennasassociated with each receiver to enhance communications between a WAPand wireless device. One such multiple antenna system is multipleinput/multiple output (MIMO). MIMO technologies offer significantincreases in data throughput and link range without additional bandwidthor increased transmit power.

In a MIMO system the transmitter sends multiple streams from multiplebase antennas. The transmitted streams define a number of paths betweenthe base antennas at the transmitter and the device antennas at thereceiver. The transmit streams may be represented as a matrix asillustrated in FIG. 1, a simple MIMO system 30 having a transmitter 32with two base antennas 36A, 36B and receiver 34 with two device antennas38A, 38B which together define four transmission paths. Systemthroughput is in a MIMO system is multiplied nearly linearly with everyadditional antenna. For example a 2×2 MIMO system as shown in FIG. 3will approximately double throughput. Full throughput enhancement in aMIMO system is only achieved however, if the additional antennastransmit in uncorrelated Rayleigh fading channels. Thus, most effectiveMIMO transmission requires that the paths between antennas bede-correlated

Path de-correlation is thus a very useful characteristic for a MIMOsystem. De-correlation increases the rank of the system, which can beestimated theoretically, and tweaked and optimized empirically. This isparticularly useful since many standards, for example Wi-Fi 802.11n,802.11ac and LTE define parameters that can be used to measure MIMOde-correlation and system rank, which can be used actively to placeantennas optimally or refine antenna placement.

MIMO performance is also dependent on good channel prediction foroptimal preconditioning, and rank estimation. The disclosed methods andsystems have an advantage because modes propagating in a duct are linkedto the physical setup of the duct work, and therefore vary little overtime.

Certain systems described in more detail below feature base antennaswhich are not necessarily close to each other, or possibly not on thesame duct cross-section. Macro-diversity within a multiple antennasystem can be achieved with antennas cabled into different ductlocations. The ducting and vent placement then contributes to thedifferent propagation characteristics for the overall system.

IV. Specific Method and System Embodiments

One embodiment is a communications system which is configured to use abuilding ventilation system as a system of waveguides thus enhancing thequality of wireless broadband coverage within the building. For example,FIG. 2 schematically illustrates a communications system 100 locatedwithin a building 102. The communications system includes at least onetransmitter 104. The transmitter 104 can be, but is not limited to, awireless access point (WAP) such as a wireless router. The transmittercould be a Wi-Fi hotspot, a base station, a cellular repeater, a smallcell, a distributed antenna system (DAS), nodes of a heterogeneousnetwork (HetNet), or another device which transmits data over radiofrequencies. The transmitter 104 is thus enabled to transmit a radiofrequency signal according to an IEEE standard. For example thetransmitter 104 may transmit a wireless broadband signal according tothe 802.11a/b/g/n, 802.11ac, LTE, or LTE Advanced, 802.16 WiMAX, 802.20MBWA or other standards.

It may be noted from FIG. 2 that the transmitter 104 is associated withand transmits through multiple base antennas 106. Furthermore, the baseantennas 106 are inserted into or within one or more ducts 108 of theventilation system 110 of the building 102. The communications system100 also includes one or more receivers 112. A receiver 112 is definedas any wireless device configured to communicate wirelessly with thetransmitter 104. Thus the receiver 112 could be a personal computer112A, laptop computer 112B, tablet computer 112C, a cell phone or smartphone 112D, a PDA, a smart thermometer 112E, a television, video playeror recording device, a smart appliance, and alarm system, a printer, acopier, a fax machine or any other device configured to receive andtransmit wireless broadband communications.

As shown on FIG. 2, the receivers 112 may be distributed throughout thebuilding 102 with any number of walls 114, floors 116 or ceilingsposition between a given receiver 112 and the transmitter 104 andantenna 106. Broadband wireless signals transmitted from the transmitter104 and antenna 106 are at least in part guided through the ventilationsystem 110 by the ducts 108 acting as hollow waveguides. The ducts 108may in certain instances be leaky waveguides which allow a portion ofthe wireless signal to pass outside of the ducts through the duct walls.More typically however, as shown in FIG. 2, the ventilation system 110will include multiple vents 118 or other openings providing for airexchange with the various rooms of the building 102. Two-way wirelesscommunication may occur between the transmitter 104 one or morereceivers 112 through the vents 118 of the ventilation system 110.

As also illustrated on FIG. 2, the transmitter 104 is typicallyconnected to at least one wired network 120 which may be located insideof or outside of the building 102. Typically, the transmitter 104 isconnected to the wired network 120 with one or more electrical oroptical cables and one or more intermediate devices. The wired network120 can be any network including but not limited to a local area network(LAN), a wide area network (WAN), part of a DAS, HetNet, or small cellbackhaul network, the Internet, a cellular telephone communicationsnetwork or a combination of networks. For example, the transmitter 104may be attached to a LAN which is then attached to the Internet througha dedicated data communications line, a DSL modem 122, a cable modem orother supplemental infrastructure. The system 100 may include any numberof supplemental or peripheral elements including but not limited to acomputer 124 in wired communication with the system 100.

In FIG. 2 the transmitter 104 is shown placed outside of a portion ofthe ventilation system 110. This configuration is not limiting. Asalternatively shown in FIG. 3 and FIG. 4, the transmitter 104 may belocated inside of a duct 108 or other element of a building ventilationsystem 110 along with multiple base antennas 106. See also FIG. 5 for amore detailed view of a transmitter placed outside of a portion of theventilation system 110. Specific strategies for locating the baseantennas 106 to enhance communication of the wireless broadband signalfrom the transmitter to the receiver are described in detail below.

As noted above, each base antenna can be described as having severalconfiguration parameters. Antenna configuration parameters include, butare not limited to, the physical location of a base antenna within aduct or with respect to other base antennas. Alternatively, the angularorientation of a base antenna with respect to a duct surface or anotherantenna is a configuration parameter. In addition, certaincharacteristics of the RF signal transmitted from a base antenna can bemodified. These signal modifications are also antenna configurationparameters. Signal characteristics which can be modified includetransmission signal phase and transmission signal amplitude. Inaddition, preconditioning parameters can be applied to the signal.Preconditioning is useful in optimizing the sending of multiple signalsencoding independent data streams over different antennas. Generally,preconditioning consists in sending linear combinations of the signals,rather than the signals themselves, these linear combinations can beoptimized for the various propagation characteristics of the propagationpaths.

As detailed below, initial selection or subsequent adjustment of one ormore antenna configuration parameters may be used to enhancecommunication of the wireless broadband signal from the transmitter to areceiving device. Initially, it may be noted from FIGS. 3-5 that a givenbase antenna 106 may be located at a select distance X₀ from a verticalduct wall 126 or a select distance Y₀ from a horizontal duct wall 128.In addition the distance between selected base antennas 106 may bevaried in any direction. Furthermore, the angular orientation a of oneor more base antennas 106 may be varied with respect to the angularorientation of other antennas or the duct walls. Although illustratedwith respect to a representative duct having a rectangularcross-section, the foregoing general concepts are equally applicable toducts having a circular cross-section.

The selection or modification of antenna configuration parameters canenhance communication of the wireless broadband signal in one or morecomplementary ways. As noted above, and described in detail below, theselection and placement of multiple base antennas can facilitate thepropagation of the wireless signal in one or more higher order TE or TMmodes which are better suited for propagation through a somewhatconvoluted ventilation system 110. In addition, base antenna selectionand placement can facilitate the correlation between at least two signalpaths and/or optimize a correlation matrix between multiple baseantennas and multiple device antennas.

In a typical waveguide, the exact placement of excitation is a matter ofimpedance matching. In a wireless system, the placement of the antennamonopole follows similar rules plus the need to consider the generationor optimization of propagating modes. It may be noted that in a multipleantenna system, placement and spacing affects modes; modes are somewhatorthogonal, which add to de-correlation, which is important to MIMO. Theamplitude/phase choices may be setup as in a smart antenna, with afeedback mechanism that allows for optimal choice. The feedbackmechanism can be a very complex iterative process in MIMO.

In view of the foregoing discussion of modal field distribution, thefollowing rules may be stated for optimal antenna placement in arectangular waveguide such as a duct.

-   -   Place antennas a distance of a/m apart when in opposite phase.    -   Place antennas a distance of a/(2m) away from a metallic duct        wall when in opposite phase.    -   Place antennas a distance of (2a)/m apart when in phase.    -   Place antennas a distance of a/(2m) away from a metallic duct        wall when in phase.        -   Where (a) is the width of the duct and m is the desired            transverse electric mode.            As noted above, the selection or modification of antenna            configuration parameters can enhance broadband signal            transmission in more than one complementary way. Thus, in            addition to the use of multiple base antennas as described            above to excite desirable transmission modes, the multiple            base antennas can be configured to promote de-correlation            between transmission paths between multiple base and device            antennas. De-correlation increases the rank of the system,            which can be estimated theoretically, and adjusted or            optimized empirically. This is particularly useful since            many standards, for example Wi-Fi 802.11n, 802.11ac and LTE            define parameters that can be used to measure MIMO            de-correlation and system rank, which can then be used to            place antennas optimally or refine antenna placement.

As an alternative to empirical antenna placement optimization, optimizedplacement may be accomplished through an iterative trial and errorprocess, in recognition of the imperfections of the ducts and branches,and difficulty or impossibility with full analysis of a given signalpath. A combination approach may be utilized as well, where initialantenna placement within a duct system is selected based upon modalanalyses, with optimal positions then being refined through an iterativetrial and error process using feedback from the communication betweenthe transmitter and selected devices. Thus, in a selectedimplementation, the antennas can be left at a pre-calculated position,or a received signal may be utilized to move and orient one or moreantennas to reach an optimal reading.

A system can also be devised where antennas are not necessarily close,or on the same duct cross section. Macro-diversity of the multipleantenna system can be achieved with antennas cabled into different ductlocations. The ducting and vent placement then contributes to thedifferent propagation characteristics of the MIMO system.

Alternative embodiments include methods of distributing a broadbandwireless signal in a building. For example, one representative method600 is illustrated in the flowchart of FIG. 6. The method 600 isinitiated by providing a system which includes a transmitter operativelyassociated with multiple base antennas where the base antennas areplaced within a building ventilation system (step 602). In addition, atleast one receiver operatively associated with one or more deviceantennas is provided within the building (step 604). The method furtherincludes initially selecting or manipulating a configuration parameterof at least one base antenna to enhance communication or transmission ofthe wireless broadband signal from the transmitter to the receiver (step606). Selecting or manipulating a configuration parameter can includebut is not limited to, selecting a physical placement location for abase antenna, selecting an antenna orientation, selecting an initialtransmission signal phase or selecting an initial transmission signalamplitude.

The method 600 may optionally further include transmitting a wirelessbroadband signal from the transmitter through the multiple base antennas(step 608) and receiving the wireless broadband signal with the receiverthrough one or more device antennas (step 610).

An alternative method 700 is illustrated in FIG. 7. The method 700 isinitially the same as the method 600, thus steps 702, 704, 706 and 708correspond to steps 02-608 above. At step 710 however, the method 700includes the step of analyzing a received signal to determine a signalparameter. Analysis can be performed on any signal attribute includingbut not limited to, signal or subcarrier power level, signal orsubcarrier signal-to-noise ratio, signal or subcarrier throughput,signal or subcarrier latency or other parameters. Analysis can be formedupon a subcarrier actively carrying data or communication symbols orpackets or analysis can be performed upon a dedicated pilot subcarrier.Alternatively, analysis can be performed on the subcarriers of adedicated training sequence.

Signal analysis can be provided by a dedicated device such as a spectrumanalyzer for signal analysis can be provided in a module associated witha wireless receiver, the transmitter or elsewhere. In any case, signalanalysis will typically be provided by a processing device 130 asdescribed in more detail below. The processing device 130 is illustratedin FIG. 2 as being associated with the transmitter 104. If theprocessing device 130 is not directly associated with the transmitter104, the results of signal analysis may be conveyed to the transmitter104.

Upon the receipt or generation of the results of signal analysis, themethod 700 may further include step 712, modifying a configurationparameter of at least one base antenna to enhance communication of thewireless broadband signal from the transmitter to the receiver. Theconfiguration parameter is thus modified in accordance with thedetermined signal parameter to enhance the signal. Modification canoccur automatically, if the signal parameter is one which can becontrolled by the processing device 130; signal phase or amplitude forexample. Alternatively, modification can occur as directed by theprocessing device 130 with any necessary user intervention. For example,a user could be directed to move the location of one or more baseantennas or adjust the angular orientation of one or more base antennas.

Steps 710 and 712 may be repeated periodically or continuously ifdesired to account for temporary or long-term changing conditions withinthe transmission environment.

FIG. 8 illustrates a method 800 which expands upon methods 600 and 700.In particular, method 800 details that steps 606 and 706 may beimplemented with one or more alternative and complementary optimizationstrategies. For example the method 800 may include optimization of thepropagation of the wireless broadband signal within the ventilationsystem (step 806). Propagation optimization may include but is notlimited to selecting or modifying an antenna configuration parameter tofavor one or more transmission modes. The method 800 may also includeoptimization of the de-correlation between at least two signal paths orthe optimization of a correlation matrix between at least two baseantennas and at least two device antennas, (steps 808 and 810respectively). It is important to note that the described optimizationstrategies and other optimization strategies are complementary and notmutually exclusive.

As noted above, certain signal analysis and processing steps may beimplemented with a processing device 130. The processing device may beincluded within a stand-alone spectrum analyzer. Alternatively theprocessing device 130 may be included within or associated with awireless device 112 or the transmitter 104. FIG. 9 provides a schematicillustration of one embodiment of a processing device 900 that can belocated as described above to perform the methods provided by variousother embodiments, as described herein. It should be noted that FIG. 9is meant only to provide a generalized illustration of variouscomponents, of which one or more (or none) of each may be utilized asappropriate. FIG. 9, therefore, broadly illustrates how individualsystem elements may be implemented in a relatively separated orrelatively more integrated manner.

The processing device 900 is shown comprising hardware elements that canbe electrically coupled via a bus 905 (or may otherwise be incommunication, as appropriate). The hardware elements may include one ormore processors 910, including without limitation one or moregeneral-purpose processors and/or one or more special-purpose processors(such as digital signal processing chips, graphics accelerationprocessors, and/or the like); one or more input devices 915, which caninclude without limitation a mouse, a keyboard and/or the like; and oneor more output devices 920, which can include without limitation adisplay device, a printer and/or the like.

The processing device 900 may further include (and/or be incommunication with) one or more storage devices 925, which can comprise,without limitation, local and/or network accessible storage, and/or caninclude, without limitation, a disk drive, a drive array, an opticalstorage device, solid-state storage device such as a random accessmemory (“RAM”) and/or a read-only memory (“ROM”), which can beprogrammable, flash-updateable and/or the like. Such storage devices maybe configured to implement any appropriate data stores, includingwithout limitation, various file systems, database structures, and/orthe like.

The processing device 900 might also include a communications subsystem930, which can include without limitation a modem, a network card(wireless or wired), an infra-red communication device, a wirelesscommunication device and/or chipset (such as a Bluetooth™ device, an802.11 device, a WiFi device, a WiMax device, a WWAN device, cellularcommunication facilities, etc.), and/or the like. The communicationssubsystem 930 may permit data to be exchanged with a network (such asthe network described below, to name one example), with other computersystems, and/or with any other devices described herein. In manyembodiments, the processing device 900 will further comprise a workingmemory 935, which can include a RAM or ROM device, as described above.

The processing device 900 also may comprise software elements, shown asbeing currently located within the working memory 935, including anoperating system 940, device drivers, executable libraries, and/or othercode, such as one or more application programs 945, which may comprisecomputer programs provided by various embodiments, and/or may bedesigned to implement methods, and/or configure systems, provided byother embodiments, as described herein. Merely by way of example, one ormore procedures described with respect to the method(s) discussed abovemight be implemented as code and/or instructions executable by acomputer (and/or a processor within a computer); in an aspect, then,such code and/or instructions can be used to configure and/or adapt ageneral purpose computer (or other device) to perform one or moreoperations in accordance with the described methods.

A set of these instructions and/or code might be encoded and/or storedon a non-transitory computer readable storage medium, such as thestorage device(s) 925 described above. In some cases, the storage mediummight be incorporated within a computer system. In other embodiments,the storage medium might be separate from a computer system (i.e., aremovable medium, such as a compact disc, etc.), and/or provided in aninstallation package, such that the storage medium can be used toprogram, configure and/or adapt a general purpose computer with theinstructions/code stored thereon. These instructions might take the formof executable code, which is executable by the processing device 900and/or might take the form of source and/or installable code, which,upon compilation and/or installation on the processing device 900 (e.g.,using any of a variety of generally available compilers, installationprograms, compression/decompression utilities, etc.) then takes the formof executable code.

It will be apparent to those skilled in the art that substantialvariations may be made in accordance with specific requirements. Forexample, customized hardware (such as programmable logic controllers,field-programmable gate arrays, application-specific integratedcircuits, and/or the like) might also be used, and/or particularelements might be implemented in hardware, software (including portablesoftware, such as applets, etc.), or both. Further, connection to othercomputing devices such as network input/output devices may be employed.

As mentioned above, in one aspect, some embodiments may employ acomputer system (such as the processing device 900) to perform methodsin accordance with various embodiments of the invention. According to aset of embodiments, some or all of the procedures of such methods areperformed by the processing device 900 in response to processor 910executing one or more sequences of one or more instructions (which mightbe incorporated into the operating system 940 and/or other code, such asan application program 945) contained in the working memory 935. Suchinstructions may be read into the working memory 935 from anothercomputer readable medium, such as one or more of the storage device(s)925. Merely by way of example, execution of the sequences ofinstructions contained in the working memory 935 might cause theprocessor(s) 910 to perform one or more procedures of the methodsdescribed herein.

The terms “machine readable medium” and “computer readable medium,” asused herein, refer to any medium that participates in providing datathat causes a machine to operation in a specific fashion. In anembodiment implemented using the processing device 900, various computerreadable media might be involved in providing instructions/code toprocessor(s) 910 for execution and/or might be used to store and/orcarry such instructions/code (e.g., as signals). In manyimplementations, a computer readable medium is a non-transitory,physical and/or tangible storage medium. Such a medium may take manyforms, including but not limited to, non-volatile media, volatile media,and transmission media. Non-volatile media includes, for example,optical and/or magnetic disks, such as the storage device(s) 925.Volatile media includes, without limitation, dynamic memory, such as theworking memory 935. Transmission media includes, without limitation,coaxial cables, copper wire and fiber optics, including the wires thatcomprise the bus 905, as well as the various components of thecommunication subsystem 930 (and/or the media by which thecommunications subsystem 930 provides communication with other devices).Hence, transmission media can also take the form of waves (includingwithout limitation radio, acoustic and/or light waves, such as thosegenerated during radio-wave and infra-red data communications).

Common forms of physical and/or tangible computer readable mediainclude, for example, a floppy disk, a flexible disk, a hard disk,magnetic tape, or any other magnetic medium, a CD-ROM, any other opticalmedium, punch cards, paper tape, any other physical medium with patternsof holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chipor cartridge, a carrier wave as described hereinafter, or any othermedium from which a computer can read instructions and/or code.

Various forms of computer readable media may be involved in carrying oneor more sequences of one or more instructions to the processor(s) 910for execution. Merely by way of example, the instructions may initiallybe carried on a magnetic disk and/or optical disc of a remote computer.A remote computer might load the instructions into its dynamic memoryand send the instructions as signals over a transmission medium to bereceived and/or executed by the processing device 900. These signals,which might be in the form of electromagnetic signals, acoustic signals,optical signals and/or the like, are all examples of carrier waves onwhich instructions can be encoded, in accordance with variousembodiments of the invention.

The communications subsystem 930 (and/or components thereof) generallywill receive the signals, and the bus 905 then might carry the signals(and/or the data, instructions, etc. carried by the signals) to theworking memory 935, from which the processor(s) 905 retrieves andexecutes the instructions. The instructions received by the workingmemory 935 may optionally be stored on a storage device 925 eitherbefore or after execution by the processor(s) 910.

While certain features and aspects have been described with respect toexemplary embodiments, one skilled in the art will recognize thatnumerous modifications are possible. For example, the methods andprocesses described herein may be implemented using hardware components,software components, and/or any combination thereof. Further, whilevarious methods and processes described herein may be described withrespect to particular structural and/or functional components for easeof description, methods provided by various embodiments are not limitedto any particular structural and/or functional architecture but insteadcan be implemented on any suitable hardware, firmware and/or softwareconfiguration. Similarly, while certain functionality is ascribed tocertain system components, unless the context dictates otherwise, thisfunctionality can be distributed among various other system componentsin accordance with the several embodiments.

Moreover, while the procedures of the methods and processes describedherein are described in a particular order for ease of description,unless the context dictates otherwise, various procedures may bereordered, added, and/or omitted in accordance with various embodiments.Moreover, the procedures described with respect to one method or processmay be incorporated within other described methods or processes;likewise, system components described according to a particularstructural architecture and/or with respect to one system may beorganized in alternative structural architectures and/or incorporatedwithin other described systems. Hence, while various embodiments aredescribed with—or without—certain features for ease of description andto illustrate exemplary aspects of those embodiments, the variouscomponents and/or features described herein with respect to a particularembodiment can be substituted, added and/or subtracted from among otherdescribed embodiments, unless the context dictates otherwise.Consequently, although several exemplary embodiments are describedabove, it will be appreciated that the invention is intended to coverall modifications and equivalents within the scope of the followingclaims.

What is claimed is:
 1. A method of distributing a broadband wirelesssignal in a building comprising: providing a transmitter operativelyassociated with multiple base antennas, the base antennas being insertedinto one or more ducts of a ventilation system of a building; providinga receiver operatively associated with one or more device antennas; andselecting a configuration parameter of a first base antenna to favor afirst selected hollow waveguide propagation mode; and selecting aconfiguration parameter of a second base antenna to favor a secondselected hollow waveguide propagation mode which is different than thefirst selected hollow waveguide propagation mode to emphasizede-correlation between the first selected hollow waveguide propagationmode and the second selected hollow waveguide propagation mode.
 2. Themethod of claim 1 further comprising: transmitting a wireless broadbandsignal from the transmitter through the multiple base antennas; andreceiving the wireless broadband signal with the receiver, through theone or more device antennas.
 3. The method of claim 1 wherein theselected configuration parameter of the base antenna is at least one of:a location of the antenna, an angular orientation of the antenna, atransmission signal phase, a transmission signal amplitude, or atransmission signal preconditioning.
 4. The method of claim 1 whereinthe communication of the wireless broadband signal from the transmitterto the receiver is enhanced by at least one of: optimizing thepropagation of the wireless broadband signal within the ventilationsystem; optimizing de-correlation between at least two signal pathsbetween at least two base antennas and one or more device antennas; oroptimizing a correlation matrix between at least two base antennas andat least two device antennas.
 5. The method of claim 1 wherein themultiple base antennas are inserted into one or more ducts having arectangular cross section and wherein at least one antenna is associatedwith a vertical duct wall and at least one antenna is associated with ahorizontal duct wall.
 6. The method of claim 1 wherein the multiple baseantennas are inserted into one or more ducts having a rectangular crosssection and wherein two or more of the multiple base antennas areassociated with the largest horizontal duct wall.
 7. The method of claim6 wherein the two or more base antennas associated with the largesthorizontal duct wall are positioned to have different angularorientations.
 8. The method of claim 1 wherein a first base antenna isinserted into a first duct section and a second base antenna is insertedinto a second duct section which is physically separated from the firstduct section.
 9. The method of claim 2 further comprising: determining asignal parameter of the wireless broadband signal received by thereceiver; and modifying a configuration parameter of at least one baseantenna in accordance with the determined signal parameter.
 10. Acommunications system comprising: a ventilation system disposed within abuilding, the ventilation system comprising one or more ducts and one ormore ventilation openings; a receiver operatively associated with one ormore device antennas; a transmitter operatively associated with multiplebase antennas, the base antennas being inserted into one or more ductsof the ventilation system, the transmitter being further configured totransmit a wireless broadband signal from the transmitter through themultiple base antennas to be received by the receiver, wherein aconfiguration parameter a first base antenna is selected favor a firstselected hollow waveguide propagation mode and a configuration parameterof a second base antenna is selected to favor a second selected hollowwaveguide propagation mode which is different than the first selectedhollow waveguide propagation mode to emphasize de-correlation betweenthe first selected hollow waveguide propagation mode and the secondselected hollow waveguide propagation mode.
 11. The communicationssystem of claim 10 wherein the selected configuration parameter of thebase antenna is at least one of: a location of the antenna, an angularorientation of the antenna, a transmission signal phase, or atransmission signal amplitude, or a transmission signal preconditioning.12. The communications system of claim 10 wherein the communication ofthe wireless broadband signal from the transmitter to the receiver isenhanced by at least one of: optimizing the propagation of the wirelessbroadband signal within the ventilation system; optimizingde-correlation between at least two signal paths between at least twobase antennas and one or more device antennas; or optimizing acorrelation matrix between at least two base antennas and at least twodevice antennas.
 13. The communications system of claim 10 wherein themultiple base antennas are inserted into one or more ducts having arectangular cross section and wherein at least one antenna is associatedwith a vertical duct wall and at least one antenna is associated with ahorizontal duct wall.
 14. The communications system of claim 10 whereinthe multiple base antennas are inserted into one or more ducts having arectangular cross section and wherein two or more of the multiple baseantennas are associated with the largest horizontal duct wall.
 15. Thecommunications system of claim 10 wherein a first base antenna isinserted into a first duct section and a second base antenna is insertedinto a second duct section which is physically separated from the firstduct section.
 16. The communications system of claim 10 furthercomprising: a processor; and a non-transitory machine readable mediumhaving encoded thereon a set of instructions executable by the processorto perform one or more operations, the set of instructions comprising:instructions to determine a signal parameter of the wireless broadbandsignal received by the receiver; and instructions to modify aconfiguration parameter of at least one base antenna in accordance withthe determined signal parameter.
 17. The communications system of claim10 wherein the transmitter is located within a duct.
 18. Thecommunications system of claim 10 wherein the transmitter is locatedoutside of a duct and communicates the wireless broadband signal to theantennas through conductors.